This invention relates to a centrifuge for separating liquids, comprising a rotor in the form of a body having rotational symmetry and having a surface through which a plurality of socket-type holes open, for accommodating respective substantially cylindrical vessels. The holes each lie in respective plans normal to the axis of rotation of the rotor at the angular points of a regular polygon. The rotor is designed to be mounted to a motor for rotating the rotor at a speed of many tens of thousands of revolutions per minute.
A centrifuge of this kind, also called a biomedical centrifuge, is known, e.g. from U.S. Pat. No. 3,248,046. The rotor of the known biomedical centrifuge is a substantially solid body. When the holes in the rotor are at a fixed angle to the axis of rotation, the rotor is called a "fixed-angle rotor". When the central axes of the holes are parallel to the axis of rotation, the rotor is called a "vertical rotor". In operation, cylindrical vessels, filled with liquid to be treated, are placed in the holes of the rotor. Upon rotation of the rotor, liquid particles of a larger specific mass will move relatively to liquid particles of smaller specific mass in the direction of the centrifugal accelaration, thereby effecting the desired separation.
Knwon centrifuges rotate at speeds of some tens of thousands of revolutions per minute, up to as much as about 70,000 r.p.m. and a centrifugal acceleration, in m/sec.sup.2, of up to 500,000 g. The rotor should then be able to resist the centrifugal force exerted on the rotor by each vessel with liquid to be separated, as well as the liquid pressure produced in a vessel. To that end, the rotor consists mostly of an alloy of aluminum or of titanium, or as proposed in the above identified U.S. patent, of a mass of layers of glass fibre impregnated with a resinous binder. Such materials have a low density, which is important for proper handling and high strength, which together with low density, is important for a high centrifugal acceleration.
A drawback of the known centrifuges is that the choice of the design limits the maximum number of revolutions per minute. In spite of the fact that the above-identified U.S. patent suggests that the rotor proposed therein permits one to attain speeds of up to 100,000 r.p.m., this appears not to have been realized in actual practice. Besides, the rotor in the known centrifuges is heavy, so that its handling is adversely affected, as well as the so-called run-up and run-down times.